The present application relates to bonding hard composites to polycrystalline materials, including but not limited to, polycrystalline diamond (“PCD”) materials and thermally stable polycrystalline (“TSP”) materials.
Drill bits and components thereof are often subjected to extreme conditions (e.g., high temperatures, high pressures, and contact with abrasive surfaces) during subterranean formation drilling or mining operations. Hard materials like diamond, cubic boron nitride, and silicon carbide are often used at the contact points between the drill bit and the formation because of their wear resistance, hardness, and ability to conduct heat away from the point of contact with the formation.
Generally, such hard materials are formed by combining particles of the hard material and a catalyst, such that when heated the catalyst facilitates growth and/or binding of the hard material so as to bind the particles together to form a polycrystalline material. However, the catalyst remains within the body of the polycrystalline material after forming. Because the catalyst generally has a higher coefficient of thermal expansion than the hard material, the catalyst can cause fractures throughout the polycrystalline material when the polycrystalline material is heated (e.g., during brazing to attach the polycrystalline material to the drill bit or a portion thereof like a cutter or during operation downhole). These fractures weaken the polycrystalline material and may lead to a reduced lifetime for the drill bit.
To mitigate fracturing of the polycrystalline material, it is common to remove at least some of the catalyst, and preferably most of the catalyst, before exposing the polycrystalline material to elevated temperatures. Polycrystalline materials that have a substantial amount of the catalyst removed are referred to as thermally stable polycrystalline (“TSP”) materials.
Specifically for drill bits, TSP materials are often bonded to another material (e.g., a hard composite like tungsten carbide particles dispersed in a copper binder) to allow the more expensive TSP materials to be strategically located at desired contact points with the formation. However, separation of the TSP material and the surface to which it is bonded during operation reduces the efficacy and lifetime of the drill bit.